An illumination control system has been known which is configured so as to turn on an illumination apparatus when it is determined that a person is present in an illumination space based on an image captured by an image sensor. An illumination controller included in the illumination control system switches the mode between a first mode in which the presence or absence of a person in the illuminated space is detected by using the image sensor and a second mode in which the brightness of the illumination space is detected by using the image sensor. Therefore, in the first mode, the illumination controller changes an ON/OFF state of the illumination apparatus if the presence of a person is detected, and in the second mode, the illumination controller controls the dimming of the illumination apparatus such that an average luminance value of the captured image falls within in a target range (see, e.g., Japanese Unexamined Patent Application Publication No. 2014-102909).
The illumination controller performs both the detection of the presence of a person and the detection of the brightness by using the image sensor. However, in each case, the setting of the image sensor is different. In the case of detecting the presence of a person, an amplification factor is controlled adaptively in order for the captured image to have optimal brightness. However, in the case of detecting the brightness, the amplification factor is fixed in order to detect the brightness itself of the captured image. Therefore, the detection of the presence of a person and the detection of the brightness are not performed at the same time.